In process automation technology, field devices are often applied, which serve for registering and/or influencing process variables. Examples of such field devices are fill level measuring devices, mass flow measuring devices, pressure- and temperature measuring devices, etc., which, with corresponding sensors, register the process variables, fill level, flow, or temperature.
For influencing process variables, so-called actuators are used. For example, valves influence the flow of a liquid in a section of pipeline or pumps influence the fill level in a container.
Various such field devices are produced and sold by the group of companies, Endress+Hauser.
As a rule, field devices in modern automation technology plants are connected via fieldbus systems (HART, Profibus, Foundation Fieldbus) with superordinated units. These superordinated units serve for, among other things, process control or process visualizing.
Besides process control and process visualizing, fieldbus systems serve also for monitoring process plants. A plant monitoring can occur, for example, with the assistance of a corresponding process control unit (for example Simatic S7, of the firm, Siemens). Process control units obtain plant-relevant data via telegrams, which are transmitted via the fieldbus in regular (cyclic/scheduled) data traffic.
Monitoring-relevant information is frequently obtained with the assistance of process models, which perform a comparison between actual values and desired values.
Normally process models are parts of monitoring applications which are integrated in process control applications.
A disadvantage of monitoring applications integrated in process controllers is that there is a strong dependence on the manufacturers of the process control units. Changes/adaptations cannot be directly performed by the user. Furthermore, all changes and optimizations with respect to the monitoring application always have an effect on the process control application (e.g. performance, reliability, etc.).
Besides such integrated solutions, separated monitoring applications are also known. An example for this is the product FieldCare of the firm, Endress+Hauser. In such case, the data needed for the monitoring application are exchanged not via regular data traffic but instead via non-regular (acyclic/unscheduled) data traffic. This data must be queried from the field devices supplementally to the cyclic data. Besides process information, the monitoring applications also evaluate particular device diagnosis information from the individual field devices. Also, in such case, process models are frequently applied that compare actual values with desired values.
In relatively simple monitoring applications, only the diagnostic information delivered by the field devices is evaluated. In more comprehensive applications, however, process models are also taken into consideration.
Such separated monitoring applications have the disadvantage that the corresponding information must be queried supplementally via the fieldbus, which naturally leads to an additional load on the fieldbus due to the increased bus traffic.